Health care workers and carers >18 years in the UK could get any vaccine relatively early on. Because of the Pfizer storage requirements, it was used largely in hospital vaccination sites. So in UK, hospital staff largely got Pfizer in contrast to Norway/Germany who got AZ. 1/4
https://twitter.com/ajamjm/status/1398544617805467648
In the UK this was a logistics issue since prior to March we knew nothing about VITT. Many European countries felt the efficacy data for the AZ vaccine were not strong for >65, so gave Pfizer to >65 and AZ to <65. 2/4
In Norway and Germany where the decision was to use AZ for <65 years, they also decided to give it to health care staff first. Since health care staff are more likely to be female, there was a large female excess in the persons who developed VITT. 3/4
All of this emphasises the point that to be able to calculate risk you need to know the number including age and sex of the affected (with VITT) and the number with age and sex breakdown of the exposed (to the AZ vaccine). 4/4
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